Blueberry Species Research Articles

Regulation of gene expression in roots of the pH-sensitive Vaccinium corymbosum and the pH-tolerant Vaccinium arboreum in response to near neutral pH stress using RNA-Seq

BackgroundBlueberries are one of the few horticultural crops adapted to grow in acidic soils. Neutral to basic soil pH is detrimental to all commonly cultivated blueberry species, including Vaccinium corymbosum (VC). In contrast, the wild species V. arboreum (VA) is able to tolerate a wider range of soil pH. To assess the molecular mechanisms involved in near neutral pH stress response, plants from pH-sensitive VC (tetraploid) and pH-tolerant VA (diploid) were grown at near neutral pH 6.5 and at the preferred pH of 4.5.ResultsTranscriptome sequencing of root RNA was performed for 4 biological replications per species x pH level interaction, for a total of 16 samples. Reads were mapped to the reference genome from diploid V. corymbosum, transforming ~55% of the reads to gene counts. A quasi-likelihood F test identified differential expression due to pH stress in 337 and 4867 genes in VA and VC, respectively. Both species shared regulation of genes involved in nutrient homeostasis and cell wall metabolism. VA and VC exhibited differential regulation of signaling pathways related to abiotic/biotic stress, cellulose and lignin biosynthesis, and nutrient uptake.ConclusionsThe specific responses in VA likely facilitate tolerance to higher soil pH. In contrast, response in VC, despite affecting a greater number of genes, is not effective overcoming the stress induced by pH. Further inspection of those genes with differential expression that are specific in VA may provide insight on the mechanisms towards tolerance.

Differential iridoid production as revealed by a diversity panel of 84 cultivated and wild blueberry species.

Cultivated blueberry (Vaccinium corymbosum, Vaccinium angustifolium, Vaccinium darrowii, and Vaccinium virgatum) is an economically important fruit crop native to North America and a member of the Ericaceae family. Several species in the Ericaceae family including cranberry, lignonberry, bilberry, and neotropical blueberry species have been shown to produce iridoids, a class of pharmacologically important compounds present in over 15 plant families demonstrated to have a wide range of biological activities in humans including anti-cancer, anti-bacterial, and anti-inflammatory. While the antioxidant capacity of cultivated blueberry has been well studied, surveys of iridoid production in blueberry have been restricted to fruit of a very limited number of accessions of V. corymbosum, V. angustifolium and V. virgatum; none of these analyses have detected iridoids. To provide a broader survey of iridoid biosynthesis in cultivated blueberry, we constructed a panel of 84 accessions representing a wide range of cultivated market classes, as well as wild blueberry species, and surveyed these for the presence of iridoids. We identified the iridoid glycoside monotropein in fruits and leaves of all 13 wild Vaccinium species, yet only five of the 71 cultivars. Monotropein positive cultivars all had recent introgressions from wild species, suggesting that iridoid production can be targeted through breeding efforts that incorporate wild germplasm. A series of diverse developmental tissues was also surveyed in the diversity panel, demonstrating a wide range in iridoid content across tissues. Taken together, this data provides the foundation to dissect the molecular and genetic basis of iridoid production in blueberry.

Nitrogen-source preference in blueberry (Vaccinium sp.): Enhanced shoot nitrogen assimilation in response to direct supply of nitrate

Blueberry (Vaccinium sp.) is thought to display a preference for the ammonium (NH4+) form over the nitrate (NO3−) form of inorganic nitrogen (N). This N-source preference has been associated with a generally low capacity to assimilate the NO3− form of N, especially within the shoot tissues. Nitrate assimilation is mediated by nitrate reductase (NR), a rate limiting enzyme that converts NO3− to nitrite (NO2−). We investigated potential limitations of NO3− assimilation in two blueberry species, rabbiteye (Vaccinium ashei) and southern highbush (Vaccinium corymbosum) by supplying NO3− to the roots, leaf surface, or through the cut stem. Both species displayed relatively low but similar root uptake rates for both forms of inorganic N. Nitrate uptake through the roots transiently increased NR activity by up to 3.3-fold and root NR gene expression by up to 4-fold. However, supplying NO3− to the roots did not increase its transport in the xylem, nor did it increase NR activity in the leaves, indicating that the acquired N was largely assimilated or stored within the roots. Foliar application of NO3− increased leaf NR activity by up to 3.5-fold, but did not alter NO3− metabolism-related gene expression, suggesting that blueberries are capable of post translational regulation of NR activity in the shoots. Additionally, supplying NO3− to the cut ends of stems resulted in around a 5-fold increase in NR activity, a 10-fold increase in NR transcript accumulation, and up to a 195-fold increase in transcript accumulation of NITRITE REDUCTASE (NiR1) which codes for the enzyme catalyzing the conversion of NO2− to NH4+. These data indicate that blueberry shoots are capable of assimilating NO3− when it is directly supplied to these tissues. Together, these data suggest that limitations in the uptake and translocation of NO3− to the shoots may limit overall NO3− assimilation capacity in blueberry.

Comparison of the antiglycation activity of leaves of eight traditionally used wild blueberry species (Vaccinium L.) from northern Canada and Europe with their phytochemistry

Blueberry leaves (Vaccinium spp. L.) are used as a natural health product and traditional medicine for health maintenance in type-2 diabetes. In this study, seven blueberry species available to northern communities in North America and one used by the Lukomir Highlanders in Europe were assessed for phytochemical content and antidiabetic activity using an in vitro advanced glycation end product (antiglycation) assay. All Vaccinium spp. were found to have potent antiglycation activity that was greater than that of the outgroup Gaylussacia sp. Inhibitory concentrations of leaf extracts from Vaccinium spp. varied from 4.1 to 79.0 μg/mL. The activity was correlated to phenolic content, and eight phenolic metabolites were found to provide species markers. These species have potential for complementary dietary strategies for type-2 diabetics in northern communities.

LED light for in vitro and ex vitro efficient growth of economically important highbush blueberry (Vaccinium corymbosum L.)

Light-emitting diodes (LEDs) are useful for the growth of many plants, but not known for blueberry species. This study examined the effects of fluorescent lamps and 100 % red, 80 % red plus 20 % blue, 50 % red plus 50 % blue, and 100 % blue LEDs on the growth and development of highbush blueberry shoots under aseptic and non-aseptic conditions. Results revealed that monochromatic blue LEDs accumulated the highest contents of leaf chlorophylls. In contrast, monochromatic red LEDs inhibited chlorophyll accumulation, but produced the longest shoots and roots and provided high percentages of side shoot formation from ex vitro plants. Mixed LEDs, particularly 50 % red plus 50 % blue light, improved plant growth with respect to notably increased shoot and root biomass. Direct rooting of in vitro shoots under non-aseptic conditions was readily achieved using a commercial mixture of perlite and peat moss with high humidity controls. These findings obviously suggest the efficient use of LEDs to replace traditional fluorescent lamps in large-scale propagation of the highbush blueberry, and also pave the way for future studies on LEDs for standardizing micropropagation protocols to shrub crops and woody plants.

Variations in chlorogenic acid levels in an expanded gene pool of blueberries

Blueberry (Vaccinium spp.) fruit is a rich source of chlorogenic acid (CA), among other polyphenolics, which have been associated with human health maintenance and chronic disease prevention. This study was designed to examine variation in CA over a wide range of blueberry genotypes (different species and genetic backgrounds) including commercial cultivars, breeding selections and breeding populations that contributed to current commercial cultivars. Fully ripe fruit was evaluated for CA concentration in two successive years, and concentrations ranged from 33–71 and 58–139 mg/100 g (frozen fruit) in southern highbush (4×) and rabbiteye (6×) blueberry commercial cultivars, respectively. In the breeding selections (4×), which comprised an expanded gene pool, the CA ranged from 33–107 mg/100 g. Further gene pool expansion associated with the establishment of the breeding populations (4×) resulted in a wide range of CA concentrations with significant increases (up to 156 mg/100 g) compared to current commercial cultivars (4×). Ploidy level had a strong correlation (r = 0.7) with CA accumulation in the blueberry genotypes investigated in this study, and a significant positive correlation between CA level and anthocyanin level in blueberry was also observed (r = 0.30, 0.51. and 0.49 for commercial cultivars, breeding selections, and breeding populations, respectively). The large variation in CA accumulation indicated that significant genetic variation for CA exists among blueberry species which can be successfully utilized in breeding programs to aid in developing phytochemically-enhanced blueberry varieties.

Bioactive Compounds of Blueberries: Post-Harvest Factors Influencing the Nutritional Value of Products.

Blueberries, besides having commonly-recognized taste properties, are also a valuable source of health-promoting bioactive compounds. For several decades, blueberries have gained in popularity all over the world, and recent years have seen not only an increase in fresh consumption, but also in the importance of blueberries for the processing industry. Blueberry processing mostly consists of freezing and juicing. Recently, more attention has been drawn to dewatering and drying, which are promising areas for developing novel blueberry products. Processing affects each biologically-active compound in a different way, and it is still unknown what changes those compounds undergo at the molecular level after the application of different processing technologies. This work presents the most recent state of knowledge about the pre-treatment and processing methods applied to blueberries and their influence on the content of biologically-active compounds. The presentation of methods is preceded by a brief overview of the characteristics of the blueberry species, a description of the chemical composition of the fruit and a short note about the main growing areas, production volumes and the management of fruit crops.

Nutrient Assimilation in Southern Highbush Blueberry and Implications for the Field

Successful blueberry (Vaccinium sp.) cultivation typically requires soils with low pH, high organic matter, readily available iron, and nitrogen (N) in the ammonium form. Growth of blueberry on typical mineral soils (higher pH, low organic matter) is reduced. Although soil pH effects on nutrient availability and uptake are known, it is unclear if the requirement for low soil pH in blueberry production is due to effects on nutrient availability/uptake or is a more direct effect of rhizosphere pH on root function. In addition, it is unclear if the requirement for high organic matter (soil amendments) is related directly to nutrient availability/uptake. Several studies have examined the use of rootstocks to increase soil adaptation of blueberry and some of these rootstocks have been found to increase plant vigor and yield. In particular, we have investigated whether sparkleberry (Vaccinium arboreum)—a wild blueberry species that is adapted to high pH and low organic matter soils—could be used as a rootstock for commercial production of blueberry on mineral soils. Our work indicates that both nitrate (NO3−) and iron (Fe) uptake and assimilation are greater in sparkleberry compared with southern highbush blueberry [SHB (Vaccinium corymbosum interspecific hybrid)]. This is correlated with increased activity of nitrate reductase (NR) and iron chelate reductase, the rate limiting enzymes for NO3− and Fe acquisition, respectively. Field studies comparing growth and yield of own-rooted vs. grafted ‘Meadowlark’ and ‘Farthing’ SHB in amended vs. nonamended soils are ongoing. In general, own-rooted plants on amended soils exhibit greater growth than own-rooted on nonamended soils, while grafted plants in either soil system exhibit intermediate growth. Yields generally followed this pattern. Our preliminary results suggest that tolerance of SHB to mineral soils is greater when plants are grafted onto sparkleberry than when grown on their own roots. However, growth and yield of grafted plants grown under mineral soil conditions may not equal or exceed that of own-rooted plants grown under optimum soil conditions, at least in the first years after field planting. Longer term studies are necessary to fully evaluate the potential of using sparkleberry and other blueberry species as rootstocks for SHB and northern highbush blueberry (V. corymbosum).

Rhizosphere Acidification is Not Part of the Strategy I Iron Deficiency Response of Vaccinium arboreum and the Southern Highbush Blueberry

Vaccinium arboreum (VA) is a wild blueberry species that exhibits wider soil pH tolerance and greater ability for iron and nitrate uptake than cultivated Vaccinium species, including southern highbush blueberry (SHB, V. corymbosum interspecific hybrids). The ability of VA and SHB to respond to iron deficiency by rhizosphere acidification was investigated. Rooted cuttings of the VA genotype FL09-502 and SHB ‘Emerald’ were transplanted to a hydroponic system filled with complete nutrient solution. After 14 days of acclimation at 45 µm iron, plants were transferred to unbuffered nutrient solutions containing 90 or 10 µm iron. ‘Emerald’ and FL09-502 plants grown in 10 µm iron exhibited less iron uptake and lower chlorophyll, total iron, and active iron contents than plants grown in 90 µm iron. Generally, there were no species-level differences in iron or nitrate uptake. Neither FL09-502 nor ‘Emerald’ acidified the rhizosphere in either the nutrient solution or in a gel-based assay, regardless of external iron concentration. A screen of 18 additional genotypes of VA and SHB confirmed that this response is absent in these taxa. Thus, rhizosphere acidification is not part of the iron deficiency response of SHB and VA. In addition, the ability to acidify the soil is not likely to be responsible for the wider soil pH tolerance of VA.

Blueberry Culture and Pest, Disease, and Abiotic Disorder Management during Nursery Production in the Southeastern U.S.: A Review

The genus Vaccinium represents an increasingly important group of plants for the U.S. green industry. In 2012, blueberries (Vaccinium sp.) ranked the second most important berry crop in the U.S. with a total crop value over $780 million. The popularity of blueberries creates opportunities as well as challenges for nursery crop producers. This article presents a review of current nursery production practices of blueberry and explores the challenges and opportunities for nursery crop producers, including pesticide use during nursery production of an edible crop, and discusses current research relevant to the green industry. Needs for additional research and opportunities for breeding are presented. Blueberries are Ericaceous plants and have very specific cultural requirements. This review presents the culture, as well as insect, mite, and disease control from an integrated pest management (IPM) approach for several blueberry species. A serious threat to the blueberry market, spotted wing drosophila (Drosophila suzukii Matsumura) is discussed to provide information needed by commercial producers and landscape managers to address client and customer questions. This review also highlights the most relevant blueberry selections for container production in the southeastern United States.

Phenolic acids of the two major blueberry species in the US Market and their antioxidant and anti-inflammatory activities.

Highbush (cultivated) and lowbush (wild) are the two major blueberry species in the US market. Eight phenolic acids were detected and quantified from these two species by HPLC-MS. Chlorogenic acid was found to be the predominant phenolic acid in both species, with 0.44 mg/g fresh weight in lowbush blueberries and 0.13 mg/g fresh weight in highbush blueberries. Total phenolic content in lowbush blueberries is over three times higher than that of highbush blueberries. The phenolic acid mixtures representing those in the two species were prepared by using authentic standards to assess their contribution to total antioxidant and anti-inflammatory activities of the whole berries. Neither lowbush nor highbush blueberry phenolic acid mixture contributed significantly to the total antioxidant capacity of their relevant whole berries measured by oxygen radical absorbance capacity (ORAC). Both phenolic acid mixtures were able to enter the cell and showed in cell antioxidant activities from the cell based antioxidant protection of erythrocytes (CAP-e) assay. Lowbush blueberry phenolic acid mixture was found to show anti-inflammatory activities by inhibiting the nuclear factor-κB (NF-κB) activation and the production of inflammatory cytokines (TNF-α and IL-6) at the high dose.

Anthocyanin composition of different wild and cultivated berry species

A broad range of anthocyanins (glycosides of cyanidin, pelargonidin, peonidin, delphinidin, malvidin, and petunidin) was identified and quantified in the fruit of 24 wild and cultivated berry species using HPLC-DAD-MS2. The anthocyanin composition in species of Ribes, Rubus, Vaccinium, and Fragaria genus as well as in less known species of Crataegus, Morus, Amelanchier, Sorbus, Sambucus and Aronia genus was determined. Cyanidin was the most commonly occurring anthocyanidin, meanwhile malvidin glycosides were only detected in blueberries. Glycosides of pelargonidin were detected in raspberries, strawberry, black mulberry and chokeberry. Peonidin glycosides were identified in hawthorn, black currant and gooseberry as well as in blueberry species. The richest species in the content of peonidin glycosides were blueberries. Delphinidin glycosides were the prevailing form of anthocyanins in black currant and bilberry. The highest total anthocyanin content was determined in dark colored fruit of cultivated elderberry and bilberry whereas light-colored dog rose and Chinese hawthorn fruit had the lowest anthocyanin content. The composition of anthocyanidin glycosides did not differ between the fruit of wild growing and cultivated species, but their contents were generally different.

Impact of Interspecific Introgression on Anthocyanin Profiles of Southern Highbush Blueberry

Blueberry (Vaccinium L. section Cyanococcus Gray), a rich source of polyphenolics with important implications for human health and chronic diseases, has become a major fruit commodity in the United States. This study was designed to assess the impact of introgression through interspecific hybridization on anthocyanin (ANC) profiles among blueberry species. Southern highbush blueberry (V. corymbosum L.) and rabbiteye blueberry (V. virgatum Ait.) commercial cultivars, North Carolina blueberry breeding selections, and blueberry breeding populations with varying degrees of introgression from multiple species were used to address this question. The breeding selections and populations were created and selected for traits not directly related to their ANC profiles and are therefore likely representative of the current selection objectives of most public and private breeding programs. Ripe fruit at a uniform stage of maturity were evaluated for ANC concentration and profile in 2 consecutive years (2010 and 2011) from all plants. Total ANC ranged from 189 to 464, 74 to 421, and 227 to 537 mg/100 g (frozen fruit) in the commercial cultivars, breeding selections, and breeding populations, respectively. Significant increases in total ANC were observed among material that represents an expanded gene pool in southern highbush blueberry (introgression from V. angustifolium Ait., V. elliottii Chap., V. myrsinites Lam., V. pallidum Ait., V. tenellum Ait., V. fuscatum Ait., V. constablaei Gray, and V. arboreum Mar.). Differences in acylation and glycosylation patterns were also observed in the same material, which may condition relative stability, absorption, and bioavailability of ANC. Results suggest that the expansion of the gene base through interspecific hybridization can have both a positive and negative impact on ANC accumulation and that breeders need to be aware of these issues early in the breeding program.

Correlation between Species-Specific Metabolite Profiles and Bioactivities of Blueberries (Vaccinium spp.)

Metabolite profiling of three blueberry species (Vaccinium bracteatum Thunb., V. oldhamii Miquel., and V. corymbosum L.) was performed using gas chromatography-time-of-flight-mass spectrometry (GC-TOF-MS) and ultraperformance liquid chromatography-quadrupole-time-of-flight-mass spectrometry (UPLC-Q-TOF-MS) combined multivariate analysis. Partial least-squares discriminant analysis clearly showed metabolic differences among species. GC-TOF-MS analysis revealed significant differences in amino acids, organic acids, fatty acids, sugars, and phenolic acids among the three blueberry species. UPLC-Q-TOF-MS analysis indicated that anthocyanins were the major metabolites distinguishing V. bracteatum from V. oldhamii. The contents of anthocyanins such as glycosides of cyanidin were high in V. bracteatum, while glycosides of delphinidin, petunidin, and malvidin were high in V. oldhamii. Antioxidant activities assessed using ABTS and DPPH assays showed the greatest activity in V. oldhamii and revealed the highest correlation with total phenolic, total flavonoid, and total anthocyanin contents and their metabolites.

Correlation between Species Specific Metabolite Profiling and Bio-Activities of Blueberries (Vaccinium sp.)

Metabolite profiling of three different Blueberries (Vaccinium bracteatum Thunb., Vaccinium oldhami Miquel., and Vaccinium corymbosum L.) was performed using gas chromatography-time of flight-mass spectrometry (GC-TOF-MS) and ultra performance liquid chromatography-quadrupole-time of flight-mass spectrometry (UPLC-Q-TOF-MS). Multivariate analysis such as principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) clearly showed the metabolic difference according to species. Sugars were significantly different metabolites in three different blueberry species by GC-TOF-MS analysis. In UPLC-Q-TOF-MS analysis, anthocyanins and phenolic metabolites were mainly identified in blueberry samples. In particular, antocyanins were the major metabolites distinguishing two different species, Vaccinium bracteatum Thunb. and Vaccinium oldhami Miquel. The content of antocyanins such as cyanidin 3-arabinoside, cyanidin 3-O-glucoside, and peonidine 3-O-galactoside was high in Vaccinium bracteatum Thunb., while glycosides of delphinidine, petunidin, and malvidine were high in Vaccinium oldhami Miquel. Antioxidant activities assessed by ABTS and DPPH assays showed the greatest activity in Vaccinium oldhami Miquel and presented the highest correlation with total phenolic content, total flavonoid content, total anthocyanin content, and their metabolites.

Antioxidant and Metabolite Profiling of North American and Neotropical Blueberries Using LC-TOF-MS and Multivariate Analyses

There are many neotropical blueberries, and recent studies have shown that some have even stronger antioxidant activity than the well-known edible North American blueberries. Antioxidant marker compounds were predicted by applying multivariate statistics to data from LC-TOF-MS analysis and antioxidant assays of 3 North American blueberry species (Vaccinium corymbosum, Vaccinium angustifolium, and a defined mixture of Vaccinium virgatum with V. corymbosum) and 12 neotropical blueberry species (Anthopterus wardii, Cavendishia grandifolia, Cavendishia isernii, Ceratostema silvicola, Disterigma rimbachii, Macleania coccoloboides, Macleania cordifolia, Macleania rupestris, Satyria boliviana, Sphyrospermum buxifolium, Sphyrospermum cordifolium, and Sphyrospermum ellipticum). Fourteen antioxidant markers were detected, and 12 of these, including 7 anthocyanins, 3 flavonols, 1 hydroxycinnamic acid, and 1 iridoid glycoside, were identified. This application of multivariate analysis to bioactivity and mass data can be used for identification of pharmacologically active natural products and may help to determine which neotropical blueberry species will be prioritized for agricultural development. Also, the compositional differences between North American and neotropical blueberries were determined by chemometric analysis, and 44 marker compounds including 16 anthocyanins, 15 flavonoids, 7 hydroxycinnamic acid derivatives, 5 triterpene glycosides, and 1 iridoid glycoside were identified.

Relationship between polyphenol content and anti‐influenza viral effects of berries

Berries are known to have many kinds of biological activities. We focused on their antiviral effect, which has not yet been well evaluated. We compared the anti-influenza viral effects of berries belonging to the genus Vaccinium - 35 species of blueberry (Vaccinium cyanococcus), the Natsuhaze (Vaccinium oldhamii), bilberry (Vaccinium myrtillus) and cranberry (Vaccinium oxycoccos)- with those belonging to the genus Ribes, i.e. blackcurrant (Ribes nigrum). Only Elliott and Legacy among Northern Highbush varieties but many Rabbiteye varieties such as Austin, Baldwin, Brightblue, Festival, T-100 and Tifblue showed anti-influenza viral activity. Natsuhaze, bilberry, cranberry and blackcurrant had high antiviral effects. A relationship was observed between the antiviral effect and total polyphenol content. Antiviral effects were found to differ markedly between berry species. Rabbiteye varieties tended to have higher antiviral effects than Northern, Southern and Half Highbush blueberry varieties. We also found that Natsuhaze, which has recently been harvested in Japan as a potential functional food, had an antiviral effect comparable to that of bilberry, cranberry and blackcurrant. There was a positive relationship between antiviral activity and polyphenol content, indicating the possibility that polyphenol is one of the key factors in the antiviral effects of berries.

休眠前の高温・長日処理がブルーベリー3種の形態および生態に及ぼす影響

休眠前に高温・長日処理したブルーベリー3種9品種の開花時期，収穫時期，新梢成長などの生態を調査し，連続的な開花と結実を示すブルーベリーの生産法の可能性について提言した．休眠前の高温・長日処理樹は2010年11月～2011年3月まで気温10～35℃，日長15～16時間の条件下で成育した．休眠が深い‘Weymouth’，‘Bluecrop’および‘Spartan’では6月に開花し，8～9月に成熟した．なお‘Weymouth’および‘Spartan’は処理前の10月にも開花し12月に成熟したが，翌年4月までに落葉した．一方，休眠が浅く常緑性の‘Emerald’では12月から，‘Sharpblue’では翌年2月から果実が成熟し，その後も新梢の先端から基部に向かって連続的な開花と結実が生じ，これらの収穫は翌年の7月まで続いた．また，‘Magnolia’，‘Tifblue’，‘Homebell’および‘Gloria’では2～3月に開花した．従って，休眠の浅い品種では休眠前の高温・長日処理によって，オフシーズンに開花・結実すること，開花・結実が連続して生じ，収穫期間が長くなることが明らかとなった．

Effect of liquid nitrogen pretreatments on osmotic dehydration of blueberries

Fresh blueberries are highly perishable and must be preserved by either freezing or drying technologies. However, moisture impermeability of their skin is a barrier against the moisture diffusion slowing down the drying process. The aim of this study was to investigate the impact of liquid nitrogen pretreatments on osmotic dehydration kinetics of two blueberry species, Vaccinium corymbosum L. and Vaccinium angustifolium Ait, and on the physicochemical quality of dehydrated fruits.The number of immersions in liquid nitrogen was a determinant factor that accelerated water loss. Depending on the blueberry species, a reduction of dehydration time from 45% to 65% was obtained for liquid nitrogen treated samples when compared to control blueberries. Microscopic observations of the blueberry skin before and after the liquid nitrogen pretreatment revealed a decrease of the cuticle thickness, dewaxing of the skin surface and the presence of micro-fissures facilitating moisture and sugar transfer during the osmotic process. The dewaxing of the blueberry skin due to liquid nitrogen immersions was confirmed by wax quantification before and after the cryogenic pretreatments. Osmotic dehydration and liquid nitrogen pretreatments showed a slight decrease in the levels of phenolic compounds and anthocyanins compared to the fresh blueberries.

Antioxidant activities and metabolite profiling of North American and neotropical blueberries using LC-TOF-MS and multivariate analyses

North American blueberry species (Vaccinium spp.) have been studied extensively for their potential health benefits due to their high levels of polyphenolic antioxidants. There are many neotropical relatives of the blueberries and recent studies have shown that some have even stronger antioxidant activity than the well-known North American blueberry. Fourteen antioxidant marker compounds were successfully predicted by applying multivariate statistics to data from LC-TOF-MS analysis and antioxidant assays of three North American blueberry species and tweleve neotropical blueberry species. This application of multivariate analysis to bioactivity and mass data can be used for identification of markers contributing to the pharmacological activities of natural products. Also, the compositional differences between North American and neotropical blueberries were determined by chemometric analysis of LC-TOF-MS data. North American blueberries formed a distinct profile from the neotropical species, and 44 marker compounds contributing to these differences were detected.